Sundial



Patented Dec. 6, 1927 t V t es- 1. 62 UNITED? stares earner earieav srr. JOHN osn'LLIvAn, or sen Juan cnris'raeivo, CALIFORNIA.

SUNDIAIJ.

' Application. filed Deccmberlfi, 1925. Serial No. 75,711.

' 1 .This invention is a sundial that is so constructed and arranged as to indicate with approximate accuracy mean solar time or standard time instead of sundial time This 5 is accomplished by providing a sundial having a concave spherically disposed surface;

. or preferably a hemispherical bowl, that faces the celestial equatoryand a gnomon at the geometric center of the spherical surface orbowl so as to cast; a shadow spot on a chart arrangedon the concave surface or bowl. The chart has, curved lines'thereon, each of which indicates the'path ofthe shadow of the gnomon a certain time in Y every dayof the year or part of aflyear; By

having such curved line for every hour of the .day orpart thereof mean solartime will be indicated instead of sundial time.

jAnotherfeature of the invention is a sundialhavin}::twobowls arranged so that each functions during an approximate halfyear so that combined they indicate approximate mean solar, time during a complete year.

Two bowls areused in order to avoid con-.

fusion of the reversely curved lines in the charts. However in large sundials, where the charts can be combined without confusion, one bowl is sufficient. Another feature of the invention is a gnomon that will cast-a shadow with great ac:- curacy on the lines of the chart in the bowl. To the end I employ cross wires'that preferablyare united at their intersection so that the intersectionpoint is the same radial dise tance; from all points, on the concaved surface of the chart; whereby the shadow cast will be accurately and easily determined. p

The Sundial is neat and pleasing in appearance and effective and durable in use;

4Q and'automatically makes corrections between apparent solar time'and mean solar time for every 'ho ir,jhalf and quarter hours that the sun shines on it. It needs no regulationto make its timeapproximately agree to or'correspondto mean solar time; and also does not require calculations such as were formerly necessaryto determine mean solar time from sundial time.

invention.

Fig. .1 is a front view of the sundial showing. it provided with twobowls; Fig.2 is avertical cross section on line 22, Fig. 1; Fig. 3 is an enlarged diagrammatic view of lth'e Sundial shown in Fig. 1; Fig. 4 is a plan view at the sundial {when constructed onebowl, partof therim broken away; Fig.

5 is a diagrammatic plan view of one ofthe charts used when thesundial is constructed with twobowls; showing one of the developed lines associatedwithother data utilized.

for indicating mean solar time; Fig. 6 is a diagrammatic plan view ofthe chart in the other bowl that is used when the Sundial is constructed with two bowls; also showing but one of the developed lines utilized with other data toindicate-mean solar time Fig.1 7 1s a d agrammatic plan view of a chart,

with lines for hours, half hours and quarter hours indicated thereon.

The sundial shown herein .to illustratethe principles of the invention comprises a body that is preferably formed of plastic matea rial such as cement that will harden after it is shaped to form and dry; and it is pref.

erably formed with two hemispherical bowls 11 and 12 thataresubstantially' of the same a dimensions and arranged side by sideland 1 faced toward the celestial equator.

. The Sundial can be provided bowl and be formed in any way of anyisuitable material, and it need not be abowl, but a spherically concave surfaceis all that is required. The bowlh'asfa support 13 preferablyformed of brick and provided with one with a rim 14 of considerable width on which. data 15 can be inscribed, as shown, in Fig. 3; I e

or; if desired the. rim "can be left plain as shown in the other figures.v The face of the rim 14 correspondsto aplane out centrally through a sphere; and. the concave inner surfaces of the bowls cgrrespondto hemig I spheres.

A gnomon' is formed of intersecting cross wires 18, 19'secured by anchors 20 to the rim 14; and the intersection thereofis arranged at a point that is an eXactj-radial distance from all points on the concave surface of t I its respective bowl that is in the geometric center thereof: and preferably these wires 18 and 19 are united at their point of intersections so as to form a gnomon with a point adapted to cast a dist nct shadow wh chcan 1 be seen with accuracy. The accompanying drawings illustrate the predetermined times. Chart- 21 is provided withdeveloped curved lines 23 that are s Jaced one hour apart and are indicated by Charts 21: and '22 arearranged'in the bowls 11 and 12- inposition to be in-registry .with the shadowsof the gnomon at-certain t e Roma n hour numerals V11 to X11 hour'Vll at hastening ate close of the day not being shown. 'Also half-hour and quarter hour lines and 26 3, indicates approximate mean solar time nomic'al data beside the lines.

beside the dates, 1s the declination of the sun at noon "on the given dates in column A,

between December 21 of one year and June 21 of the next year. The other chart 22 in Fig. 6 and bowl 12in Fig. 3 is provided with developed curved, lines 24 that are spaced one hour apart and also indicated by the Roman hour numerals VII to XII and I to V'as is shown in the other chart and it also can have intermediate lines 25, 26 if desired, as in Fig. 7, but for the sake of clearness in the drawings and brevity they are not shown in the. other figures. This chart completes the year cycle by indicating the time from December 21 in one year to December 21 of the next year.

-When thesundial is to be constructed on ascale sui'liciently large to avoid a confusion of lines, the charts 21 and 22 can be combined as shown in Fig. 4, and when thus combined are adapted to indicate time for "a complete year.

Some lines of the charts 21 and 22 are diagrammatically illustrated in Figs. 5, 6 and .7. In Figs. 5 and 6 the development of the lines is explained by dates and astro- The data,

and in column B the equation of time, or the minutes and seconds difference between sundial time and mean solar time; and adjacent to the minute [and second spaces is the developed line 23 relative to the meridian The line EE indicates the equator; the line CC, as stated, indicates the meridian or, line on which the shadow of point of the gnomon will fall "at the noon hour of sundial time, and the curved line 23 indicates a developed line that is adapted to indicate approximate mean solar time when the gnomon shadow registers with it.

Only one line 23 is shown in Fig. 5, it being understood that there are other curved lines substantially like it foreach day hour as sho'wnin Figs. 1, 3, 4; and there can be additional lines for half hours and quarter hours as indicated in Fig. 7. As seen I therein the heavy lines 23 indicate the-hours,

the fine full lines 25 indicate the half-hours and the intermediate dotted lines 26 indicate thoseffo'r theyear 1926, the second year after leap 'year. Also the lines 23 and 24: are, for

the purpose-of illustration, here shown as the appeardeveloped on a flat surface, but for absolute accuracy-are to be and have in actual practice been developed on the concave spherically disposed surface.

It is understood that in practicethere will be eleven of each of the hour lines 23 and 24, and that between them will be arranged the half-hour and quarter hour lines 25, 26 as previously stated and as shown in Fig. 7.

For the sake of brevity and cle'arness only a small number of year dates and time-rectifying figures are given in Figs. 5 and 6 or just sufficient to illustrate how the difi'eren'cein time is computed and the time rectifying lines developed.

As seen in Fig. 5 sundialnoon time and mean solar noon time at the point 27 for December 2 1 agree; then on January 31 there is a difference of 13 minutes and 25 seconds."

In other words the pointer shadow atthe noon hour mean solar time falls on line 23 at the point 28 and at noon hour sun-dial time the shadow engages the line CC at the point 29, 13 minutes and 26's'econds later, or the difference in time previously "stated;

Again on the date of April 15's undial time and mean solartime agree; then on May 10 7 there is a difference of three minutes and'six seconds, sundial noon time beingindi'cated at the point- 30 and mean solar noon timeat the point 31. Sundial time'andmean solar time again agree on June 15, as indicated at the point 31. It is understood that the difierence in time for the other hours of the day are determined in substantially the same way as the noon hours shown in Figs. 5 and 6.

Referring now to Fig- 6 on July 29th-there is a difierence of six minutes and twenty seconds between mean solar time atth-e point 32 and sundial time at the point 33. Again September 1 the times agree at the point 34. On November 15th there is. a difference of fifteen minutes and twenty-nine seconds between sundial time at the point 35 and mean solar time at thepoint 36. v

' In other words theline's 23 and 24: and their associated lines 25, 26 are developed so that when they are engaged by a pointer shadow they indicate mean solar time for the hour or fraction of an hourtha'tthe' line represents.

The bowls '11, 12 are provided with holes 40 that are connected to drain pipes tl as ture is a spherically disposed surface or "chart. Thus the upper and lower parts of the bowl shown, above and below the chart, could be omitted, andthe dial be operative. N or must the gnomon be made of cross wires 7 on the bowl rim, as any shadow casting gnomon located by any means at the geometric center oftheeoncave chart will suffiee, although the cross wires on therim are preferable. Also either one bowl or two may be used to indicate time for the whole'year,

although the latter is'preferable.

Nor is the invention limited to use for in dicating mean solar time, as it can be used for standard time by making either of two variations from the mean solar time dial.

By making the curved lines of the chart,

either to the right'or the left of the positions herein shown, according to the difference between the standard and mean solar time of the place where the sundial is located; or by laterally tilting the bowl so the lines of the chartas shown herein will beshifted to provide for standard instead of mean solar time, 7 that is'so these lines will mark the path of the shadow .of the gnomon accordingto bowl, and cross Wires extending in an equatorial andimeridional direction respectively and secured on the rim of the bowl with},

their. intersection located at the geometric center of the bowl to serve as a gnomon.

2. A sun-dial including two hemispherical bowls located side by side and facing the ce-- lestialequator each of said'bowls being providedwith a gnomon consisting'of a pair of cross Wires, one equatorial vand the other meridional, with the intersection thereof lo-;'

cated at the geometric center of the sphere ically disposed surface, theequatorial wires of the two bowls being. in alignmentwith each other and the meridional wires thereof being parallel With'each other, and a, chart in each bowl on which a gnomon may cast a shadow and indicate the time, the chart in one of said bowls being arranged to indicate the time for one-half of a'year and the'chart in the other bowl arranged to indicateithe time for the other half of said year. i

In witness whereof, I have hereunto affixed my signature.

s'r. JOHN OSULLIVAN, 

